Research in progress deals with the genetic basis of susceptibility to cortisone-induced cleft palate in mice. Congenic strains with recombinant H-2 haplotypes are being examined to determine which subregion of the complex controls susceptibility. The possibility that H-2 gene products are able to bind glucocorticoids is being studied by attempting to inhibit dexamethasone binding with antibodies directed to various H-2 antigens.